Classes for Python

1. Reflection

2. Built-in methods

__ Name __: Special method/Built-in method in class

Double Subscript Method Magic method

1.__call__

Instantiating an object ()---->> equivalent to executing the __call__ method

Application: Used to view the execution process in the source code

　　　　　　

2.__len__ for viewing the length of an object

Len (object), the __len__ method that invokes object does not execute Len () if there is no __len__ error

　　　　　　

3.__new__------>>> Construction method

__INIT__------>>> Initialization method

Occurs before the __init__ method is executed after instantiating the object.

1. Creating a space in memory belongs to the object

2. Pass object space to self, execute __init__

3. Returning object space to the caller

The __new__ method is executed after instantiation and then __init, which opens up a new space

Creating a singleton class with the __new__ method

Singleton class: A class that has only one instanced object from start to end

　　　　　　

4.__str__ pirnt (object) can print some properties of an object directly

　　　　　　

Classes for Python